add LICENSE file and other minor changes

README.md

@@ -1,11 +1,10 @@
-*Warning! Unfinished stuff*
+Yet another image viewer.
 
 ## Uncleaned shits inside(TM):
 
  - Mixed `CR LF` and `LF`.
  - Ugly action icons.
  - For windows build, win32 APIs are used.
- - No license file provided.
  - No drag-window-border-to-resize support under non-windows platforms (I use <kbd>Meta+Drag</kbd> to resize window under my x11 desktop).
 
 ## License